<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>无标题文档</title>

<style type="text/css">
#bigbox{width:600px; height:1000px; border:black 2px solid;}
#box1{width:100px; height:100px; background:red; float:left;}
#box2{width:200px; height:200px; background:yellow; float:left;}
#box3{width:300px; height:300px; background:blue; float:left;}
/*设置浮动元素，如果前面没有浮动元素，那么就会去寻找父元素的边框，如果前面的浮动的元素，后一个浮动的元素就会去寻找前一个有设置浮动元素的边框*/

</style>

</head>

<body>
<div id="bigbox">
<div id="box1">box1</div>
<div id="box2">box2</div>
<div id="box3">box3</div>

</div>
</body>
</html>
